This is what "responsive design" used to mean. I remember being quite confused when people started using it to refer to distinct, non-responsive mobile-vs-desktop views.
For a long time I resisted this, opting instead for more surgical introduction of a breakpoint, literally at the _point_ where some part of a page's design _breaks_ (not really the etymology of the word, but it's fun to think of it this way). But it's felt like a decade-long battle against the momentum of the industry, and sometimes I just want to build things rather than fight.
A small number of global breakpoints can be a better trade-off when it means the website works better (for most people).
I've been using CSS Grid for years as my default layout method, but it doesn't magically solve all issues.
I prefer having a few fixed well defined breakpoints that having a combination explosion of places to fix and widths that I have to control when I do a changed on a component.
On my personal site I do indeed have a media query to make some tweaks when the viewport is phone-in-portrait-orientation narrow, but I try to keep them pretty minimal. I find sites that reorganize themselves at different widths ("if your browser window is 2000px across, this is a three-column display instead of two!") to be…not necessarily bad, but at best, unnecessarily clever.
I agree this is confusing, but I think we still need a term for distinct types of views. The point of the article is that, once a user has started using one particular view, it shouldn't suddenly change to a completely different view with a different layout just because the user's browser window got resized by a few pixels.
I don't think it's possible for an app to auto-detect which view the user wants to use, particularly not if the auto-detection logic allows changing views on the fly in the middle of a user session based on resizing the browser window. I think the only real solution is to have different views that each have their own distinct URL, so the user can choose which view to use. Each view can then be "responsive" within the general constraints of the layout it adopts.